Measurement of Temporal Correlations of the Overhauser Field in a Double Quantum Dot

TL;DR

This paper investigates the spectral properties of the Overhauser field fluctuations in GaAs double quantum dots, revealing a 1/f^2 dependence and suggesting decoherence mitigation via echo techniques.

Contribution

It provides the first detailed spectral analysis of Overhauser field fluctuations in double quantum dots, linking nuclear spin diffusion to observed noise spectra.

Findings

Spectral weight concentrated below 10 Hz

Spectral dependence follows 1/f^2 pattern

Decoherence can be suppressed by echo techniques

Abstract

In quantum dots made from materials with nonzero nuclear spins, hyperfine coupling creates a fluctuating effective Zeeman field (Overhauser field) felt by electrons, which can be a dominant source of spin qubit decoherence. We characterize the spectral properties of the fluctuating Overhauser field in a GaAs double quantum dot by measuring correlation functions and power spectra of the rate of singlet-triplet mixing of two separated electrons. Away from zero field, spectral weight is concentrated below 10 Hz, with 1/f^2 dependence on frequency, f. This is consistent with a model of nuclear spin diffusion, and indicates that decoherence can be largely suppressed by echo techniques.